The cyclic voltammetry of copper in base is particularly complex as not only are metal/metal oxide, e.g., normalCu/Cu2O , and oxide/oxide, e.g., Cu2O/normalCuO [and/or normalCufalse(OH)2 ], transitions involved but there are also dissolution processes, and at least one of the oxides, Cu2O , is poorly conducting, and two of the oxidation products of copper can exist in both anhydrous and hydrated forms. The reduction process in particular is complicated by the fact that with thick films, which tend to be duplex in character, the outer layer of Cu(11) material is frequently unable to react until the inner layer of poorly conducting Cu2O is reduced. Furthermore, when the outer layer of hydrous Cu(11) oxide reduces the reaction apparently involves a Cu(1) hydrous oxide intermediate or by‐product; this Cu(11) reduction process gives rise to a separate peak, Emax , for the latter being determined by the Cu/Cu(1) hydrous oxide equilibrium, below that for the normalCu/Cu2O reaction. The conditions required to produce a thick oxide film on copper in base by the potential cycling technique were investigated. While thick films of the Cu(1) hydrous oxide were not observed, this material, at quite low coverage, is believed to be an important intermediate or mediator in a variety of anodic reactions at copper electrodes in solutions of high pH.

SUMMARYThe mechanism of SO, oxidation in diluted catalytic solutions was studied. It was found that the oxidation stops after a certain pH value is reached, In the same catalytic solutions, the maximum possible SO, -formation is a linear function of the SO, partial pressure in the air.This mechanism of SO, -formation can account for observed SO,-concentrations in rain, fog, and smog only if some neutralizing cations in the aerosols or traces of NH, in the air are present. It is shown that in the latter case the system SO,-NH,-catalytic solution can explain the main features of SOTformation in our atmosphere.

The anodic behavior of copper is surprisingly complex as this element can exhibit 4 (0, +1, +2, +3) oxidation states and most of its oxides can exist in two distinct forms, anhydrous and hydrated. Hydrous oxides in general have been widely ignored, but an appreciation of their properties is essential for a complete understanding of the behavior of metals. In the present case attention was focused on the behavior of copper in base at low potentials where a minor Cu adatom/ Cu(I) hydrous oxide transition seemed to occur. Evidence for the latter included the observation that an oxide reduction peak occurred under certain conditions at ca. 0.05V (RHE); this is significantly lower than the usual value for Cu20, Cu(OH)2, or CuO reduction. Furthermore, the same value was observed for the onset (anodic sweep)/termination (cathodic sweep) potential for other reactions on copper in base, e.g., formaldehyde oxidation or copper dissolution in the presence of CN-ions. As in the case of previous work with other metals, the response for low-coverage hydrous oxide formation on copper in base is not obvious on the anodic sweep in cyclic voltammetry experiments; however, prior data from ac work provide evidence for the type of effect postulated here. The behavior of copper, as may be expected, bears a distinct similarity to that of silver and gold; similar proposals were made recently for the latter metals. The catalytic activity of copper in base at higher potentials is attributed to mediation of interfacial processes by other redox transitions in this system.

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It has been known for some time that the group Ib metals, copper, silver, and gold, are unique with regard to the magnitude of the surface-enhanced Raman spectroscopy response recorded, especially for organic bases, at the metal/solution interface. Another unique feature of these three metal electrode systems is described here; they display an adatom (M*)/ hydrous oxide transition in which the cation is in the univalent (M § state. It is suggested that these are the only metals known to date that readily yield relatively insoluble, surface-bound, univalent hydrous oxide species that behave as strong bases. The redox transition in question, M*/M(1) hydrous oxide, displays an unusual shift in potential upon altering the solution pH; this shift (previously reported for gold and silver) was monitored in the present work by recording the change in onset (anodic sweep)/termination (cathodic sweep) potential for dimethylamine borane oxidation, a reaction induced by the oxidized form of the couple acting as a mediator. It was pointed out that the two unique features of these three metals have the same basis, i.e., an array of univalent cations attached to the electrode surface.) unless CC License in place (see abstract).